WASHINGTON (AP) — Vice President Mike Pence plans to travel to Montana next week to campaign for a Republican congressional candidate running in a special election.

The vice president’s office says Friday that Pence is expected to campaign for Greg Gianforte during the weekend of May 13. Details on the trip have not yet been finalized.

Montana is holding a May 25 special election to fill the seat vacated by Ryan Zinke, who resigned from Congress earlier this year to serve as President Donald Trump’s interior secretary.

Gianforte is competing against Democrat Rob Quist and Libertarian Mark Wicks for the state’s only congressional seat.

Trump’s son Donald Trump Jr. is campaigning for Gianforte next week, making his second trip on the GOP candidate’s behalf.

Pence’s trip was first reported by The Washington Post.